Gas lift valve apparatus

ABSTRACT

A gas lift valve used with well tubing, said valve employing a bellows means, pilot valve, and a power valve, the pilot valve being unconnected with the bellows means and differentially operated with a spring assist.

1 1 Mar. 27, 1973 ilnited States atent Blackwell 3,208,398 9/1965 Douglas........ ...l37/l55X 3,225,783 12/1965 Stacba....3...........,....l...........137/155 Primary Examiner-Alan Cohan Tex.

[73] Assignee: Dresser Industries, Inc., Dallas, Tex. Attorney-Robe" Mayer, Daniel Rubin, Peter Filed: Mar. 11, 1969 Murphy, Frank S. Troidl, Roy L. Van Winkle, William E. Johnson, Jr. and Roderick W. MacDonald ABSTRACT 21 Appl. No.: 806,070

[ U S C 137/155 A gas lift valve used with well tubing, said valve em- 1/08 p y g a bellows means pilot valve and a power [51] Int. Cl.

valve, the pilot valve being unconnected with the bel- [58] Field of Search lows means and differentially operated with a spring assist.

[56] References Cited 6 Claims, 2 Drawing Figures UNITED STATES PATENTS Cummings.....

PATENTEDHARZ? I975 INVENTOR HENRY W. BLACKWELL ATTORNEY GAS LIFT VALVE APPARATUS BACKGROUND OF THE INVENTION This invention relates to a valve for injecting lifting gas into a tubing string in an oil well, particularly gas lift flow valves of the pilot valve type.

This invention also relates to differentially operated valves, i.e., valves which operate when the tubing pressure reaches a sufficiently high value in relation to the casing pressure. A given tubing pressure can indicate the presence of liquid oil which can be pumped to the surface upon opening of the differential valve. The amount of liquid present for pumping to the surface can be increased by increasing the casing pressure because the differential valve will not open until the tubing reaches a certain value with respect to the casing pressure. Therefore, an increase in the casing pressure requires a consequent increase in the tubing pressure to cause operation of the differential valve.

U. S. Pat. No. 3,225,783, the disclosure of which is incorporated herein by reference, discloses a casing pressure controlled, pilot, gas lift valve wherein the pilot valve member is fixed to the bellows head so that opening of the pilot valve is automatic with retraction of the bellows head. The pilot valve can be opened by simply increasing the casing pressure, the tubing pressure remaining the same. Thus, increases in casing pressure on this valve can cause opening of the valve whether or not opening is desired.

At times more than one string of tubing is employed in a casing, each string having its own gas lift valves and each string operating under different tubing pressures. In such a situation, there can be a gas lift valve on each tubing string which is at the same vertical position in the casing and, therefore, at the same casing pressure. If these gas lift valves are both actuatable by increases in casing pressure, then it is difficult, if not impossible, to actuate one of these valves without actuating the other. However, the situation oftentimes arises wherein the tubing pressure in one string is sufficiently great to warrant actuation of its gas lift valve whereas the tubing pressure is not sufficiently great in the other string. Thus, it is very desirable to be able to actuate one gas lift valve on one string without actuating the gas lift valve on the other string.

SUMMARY OF THE INVENTION According to this invention, there is provided a pilot gas lift valve which is differentially actuated responsive to the tubing pressure and which cannot be actuated by casing pressure alone. The valves of this invention can be employed on multiple strings of tubing in a single casing wherein a plurality of valves are on different strings but at the same casing pressure. In this situation, each valve can still be individually opened as required by increases in tubing pressure in each string.

Thus, the valves of this invention have an extra dimension of versatility over casing pressure controlled pilot valves in that the valves of this invention can be employed not only where casing pressure controlled pilot valves are used, but also in multiple tubing string applications wherein a plurality of gas lift valves are at a single casing pressure but the valves must be individually opened.

The valve of this invention employs a pilot valve member which is not connected to the pressure responsive means, e.g. bellows, but which is urged into its closed position by the pressure responsive means. The pilot valve member has a resilient means associated therewith which is biased to urge the pilot valve member into the open position. The pressure responsive means is responsive to casing pressure by itself and retraction of the pressure responsive means does not cause retraction and opening of the pilot valve member. On the contrary, the casing pressure tends to urge the pilot valve member into the closed position and opening of this member is caused by the cumulative forces of the resilient means and the tubing pressure acting on the pilot valve head.

Thus, increases in casing pressure can cause retraction of the pressure responsive means but cannot cause opening of the pilot valve.

Opening of the pilot valve causes opening of the power valve and full operation of the gas lift valve.

This invention also relates to apparatus for injecting fluid into a tubing string using a combination of said tubing string and at least one gas lift valve having a pilot valve means that opens in response to tubing pressure.

Accordingly, it is an object of this invention to provide a new and improved gas lift valve. It is another object to provide a new and improved pilot gas lift valve wherein the pilot valve is differentially operated. It is another object to provide new and improved apparatus for injecting fluid into tubing to lift liquid in the tubing to the surface of a well.

Other aspects, objects, and advantages of this invention will be apparent to those skilled in the art from the disclosure and appended claims.

DETAILED DESCRIPTION OF THE INVENTION FIGS. 1 and 1A are cross-sectional, elevational views of a valve attached to a conventional mandrel, the valve representing but one embodiment of this invention.

In HO. 1, there is shown mandrel 41 having a sleevelike receptacle 42 in which the valve is carried.

The valve comprises a pressure dome housing I having a pressure chamber (dome) 2 therein. Access 'to' dome 2 is provided through a passage 3, having a conventional back pressure filler valve 3a threadedly engaged therein, and which is closed by a seal plug 4 threadedly attached therein.

Pressure dome 2 is sealed to the interior of bellows 6 and both the dome and bellows are charged with a predetermined pressure above atmospheric pressure through filler valve 3a prior to threading plug 4 into the dome housing 1.

A partition 5 is secured in the lower end of dome 2 and bellows 6 is secured to the lower side of partition 5..

The lower end of bellows 6 is closed by bellows head 7 which includes as an integral part thereof a guide stem 8 extending upwardly through bellows 6. Guide stem 8 includes a suspension stem 9 movably extending through a central passage 10 in partition 5. Sufficient clearance is provided between stem 9 and partition 5 to provide free communication between dome 2 and the interior of bellows 6.

A cross head 1 1 is secured to the upper end of stem 9 and arranged to engage the upper surface of partition 5 to prevent over extension of bellows 6 in case housing 13 is removed for inspection of the bellows after the dome and bellows are charged.

The tubular bellows housing 13 is threadedly engaged at 13a to the lower end of dome housing 1 and is threadedly engaged at its lower end, 18a, to power valve housing 18.

Pilot valve stem 14 extends into bellows head 7 but is not connected to the bellows head so that the bellows head can be retracted upwardly without moving the pilot stem. This allows the bellows to be retracted by increased casing pressure while leaving the pilot valve in the closed position.

Pilot valve stem 14 extends through an axial bore in partition means 16 and 16a. Partition means 16 and 16a are a pair of spaced apart backup rings carried by housing 13. Valve stem 14 also extends through an axial bore in resilient seal ring which is supported by partition means 16. Backup ring 16 is integral with the lower part of bellows housing 13. Backup ring 16a can be integral with housing 13 like ring 16 or can be separate from housing 13 for ease of removal from housing 13.

Pilot valve stem 14 has a support shoulder 50 therearound generally facing towards bellows head 7. Shoulder 50 would contact bellows head 7 but for spacing rings 51. One or more spacing rings can be employed, their function being to stop the downward movement of bellows head 7 before crosshead 11 reaches partition 5, thereby insuring a space between crosshead l1 and partition 5.

Pilot valve stem 14 carries an encircling holding means 52 which is an annular flange member that can be moved along the axial length of stem 14 by release of set screw 53. Between partition 16a and hold means 52 is disposed resilient means 54 which is a helical spring encircling stem 14 and biased so as to urge stem 14 upwards into an open position. if desired, hold means 52 can threadedly engage stem 14 for axial adjustment of resilient means 54.

Lateral pilot casing ports 43 provide access for casing pressure to retract bellows 6 by forcing bellows head 7 upward, and to urge stem 14 downward into the closed position against the force of spring 54.

Seal means 15 compartmentalizes the area above partition 16 and below bellows head 7 by contacting stem 14 but without providing a perfect seal with stem 14. Seal 15 can be a resilient seal of rubber or plastic composition such as polytetrafluoroethylene which seals but not perfectly so that pressure can gradually leak by the seal to equalize the pressure on each side thereof after a definite period of time. it is important to note that the seal does not allow substantially instantaneous equalization of pressure on both sides but rather requires a definite period of time before equalization of pressure is obtained.

Power valve housing 18 is threadedly attached to power valve seat housing 29 at 18b.

Power valve stem 19 has a restricted, axial bore 20 therethrough and is terminated at its upper end with piston head 23 containing downwardly facing shoulder 23a. in the upper surface of piston head 23 is provided an annular pilot valve seat 21 which defines the pilot valve port 210 and against which the'pilot valve head (ball) 22, secured to the lower end of pilot valve stem 14, may come into sealing contact when stem 14 is in the closed position.

Another seal means similar in composition and function to seal means 15 is carried by and around piston head 23 as shown at 24. Seal ring 24 slidably engages the inner wall of housing 18 and provides a slidable, imperfect seal with housing 18 thereby providing a resilient seal by which pressure will gradually leak until, after a finite period of time, pressure equalization is obtained on each side of seal 24.

There is thus defined above seal 24 and below seal 15 a semi-sealed zone 45 into which casing pressure from above seal 15 or below seal 24 can leak only gradually.

Another resilient means such as helical spring 25 is positioned between shoulder 230 on piston head 23 and an upwardly facing annular shoulder 26 on housing 18. Spring 25 is biased so as to urge power valve stem 19 upwardly into the open position.

A power valve head (ball) 27 is secured to the lower end of stem 19, said valve head having a bore 270 therethrough which has the same diameter as bore 20 through stem 19 and the axial bore 21a through seat 21. However, bore 21a through seat 21 can be smaller than bore 20 or 27a. Power valve head 27 is arranged to sealingly engage power valve seat 28 provided in the upper end of bore 30 of power valve seat 28 and housing 29. Seat 28 defines power valve port 28a which is the main port of the valve when in full operation and is normally larger in area than bores 21a, 20, and 27a.

Housing 29 is threadedly engaged at its lower end to check valve housing 31, as indicated at 29b.

Bores 20, 27a, and the bore through pilot valve seat 21 are in axial alignment. These axially aligned bores are in communication with the larger diameter bore 30 through power valve seat housing 29. Power valve head 27 seals off communication of bores 20 and 30 from lateral power valve casing ports 44 which communicate with the casing pressure in the casing annulus exteriorly of the valve assembly.

Springs 25 and 54 are contracted when the valve heads are in the closed position as shown in FIG. 1 and are expanded when the valves heads are moved off their respective seats into the open position so that both springs oppose the closing of their respectively as sociated valves after they have been opened.

The check valve attached below the power valve assembly is of conventional construction, and includes a check valve housing 31 having a shoulder 31a which provides a seat for encircling spring 33.

A hollow check valve body 32 is movably positioned in the bore of the check valve housing 31. Spring 33 biases check valve head (ball) 36 towards its seat 37. Head 36 is positioned so that it does not engage seat 37 thus permitting a low unit volume flow thereby and allowing tubing pressure from inside of mandrel 41 to be applied in bore 20 against pilot valve head 22. However, if a sudden surge or high volume flow enters the valve assembly from mandrel 41, check valve head 36 will be moved into engagement with seat 37 preventing flow therethrough in an upwardly direction.

The valve assembly is threadedly engaged in receptacle 39 of mandrel 41. Mandrel 41 is attached in and communicates with the bore of the tubing string extending down into the well. A bore 38 is provided through the check valve housing 31 for communication with passage 40 in receptacle 39 and the interior of mandrel 41.

In operation, pressure chamber 2 and bellows 6 are charged to a predetermined pressure above atmospheric and the valve assembly placed in its situs of operation in the well hole. The valve assembly in its normally closed position before operation thereof is as shown in FIGS. 1 and 1A with both the power valve and pilot .valve closed and the bellows head pushing against the pilot valve.

The casing pressure (P is then increased and when the casing pressure admitted through pilot casing'ports 43 is of sufficient force to counteract the dome pressure (P bellows head 7 is retracted from contact with spacing rings 51 by compression of bellows diaphragm The casing pressure that causes retraction of bellows head 7 also applies to pilot valve stem 14 and tends to urge the pilot valve into the closed position. However, when the tubing pressure (P,) in bore 20, working across the effective area of that bore A reaches a value sufficiently great so that this value in combination with the upward force exerted by spring 54 can counteract the casing pressure pushing downwardly on the pilot valve, the pilot valve stem 14 snaps upwardly into the open position. This is the differential operation of the pilot valve, i.e., the pilot valve does not operate until the tubing pressure reaches a desired value in relation to the casing pressure. Note that no amount ofcasing pressure can cause opening of the pilot valve. Larger casing pressures merely apply greater force on the pilot valve in its closed position and, therefore, require greater tubing pressure before the pilot valve can be opened.

When the pilot valve was closed and the valve assembly exposed to its operating casing pressure, casing pressure admitted through lateral ports 43 and 44 gradually leaked around seal rings 15 and 24 to bring semi-sealed zone 45 to the ambient casing pressure. Since the pilot valve has an assist into the open position by way of spring 54, the tubing pressure in bore is less than the casing pressure in the semi-sealed zone 45. Therefore, when the pilot valve is opened, semi-sealed zone 45 is exposed to the lower pressure in bore 20 and the pressure is rapidly equalized by decreasing the pressure in semi-sealed zone 45 to the tubing pressure obtaining in bore 20. Resilient seals 15 and 24 do not allow the rapid flow of easing pressure into semi-sealed zone 45 so that the net result is that there is a rapid decrease in pressure in semi-sealed zone 45. This decrease in pressure in semi-sealed zone 45 reduces the downward force on the power valve to the extent that it is counteracted by the upward force exerted by the easing pressure acting on piston 23 over the area of the bore of housing 18 where seal 24 contacts housing 18 less the area of bore 28a. This snaps the power valve open and the valve assembly is then in the full open and operating position.

When the power valve is opened, it receives the pilot valve head 22 in pilot valve seat 21-. Also, in this fully opened position, the pilot valve stem 14 is again in contact with bellows head 7. It can thus be seen that in the fully opened position, lateral pilot casing ports 43 are cut off from communication with the interior of mandrel 41 because the pilot valve has been closed. Thus, all the gas for pumping liquid to the surface is supplied through lateral power valve casing ports 44.

When the casing pressure is reduced below the bellows pressure by an amount equal to the cumulative force exerted by both springs and 54 divided by the effective area of the bellows (A the valve assembly snaps into the fully closed position as shown in FIGS. 1

opened with the remaining valves staying closed if the tubing pressure on that one valve reaches the required value. This cannot be accomplished with a casing pressure controlled pilot valve.

It can be seen from the above that this invention also relates to apparatus for injecting fluid into tubing in a well bore to lift liquid to the surface of the wall through the tubing by using the combination of said tubing string and at least one gas lift valve on said tubing, the gas lift valve having a pilot valve means such as 14 and 21 and apilot valve port 21a, the pilot valve means opening in response to increasing pressure within the tubing string. The opening of the pilot valve means causes the opening of the main operating port 28a of the gas lift valve for full operation of the gas lift valve. Main operating port 28a can be of larger area than pilot valve port 21a.

Reasonable variations and modifications are possible within the scope of this disclosure without departing from the spirit and scope of this invention.

The embodiments of the invention in which an exclusive property-or privilege is claimed are defined as follows:

1. A gas lift valve comprising,

a housing having an outlet passage, a first inlet port spaced from said outlet passage, and a second inlet port spaced intermediate said first inlet port and said outlet passage;

partition means intermediate said first inlet port and said second inlet port, said partition means having an axial passage therethrough;

a first valve seat intermediate said second inlet port and said outlet passage, said seat having an axia bore therethrough;

a first valve member having a valve headon one end and being movable between a closed position wherein said valve head engages said first valve seat and an open position wherein said valve head is out of engagement with said first valve seat, the end of said valve member opposite said valve head being a piston head, said piston head being spaced from said partition when said first valve member is in either the opened or closed position, said valve member, piston head, and valve head having an axial bore therethrough;

first resilient means associated with said first valve member, said first resilient means being biased to urge said first valve member into the open position;

a second valve seat carried by said first valve member piston head on the side of said piston head nearest said partition means, said second valve seat having an axial bore therethrough in alignment with the bore in said first valve member;

a second valve member having a valve head on one 3. A gas lift valve according to claim 2 wherein end, said second valve member extending through said piston head is closely spaced to said housing and the bore of said partition means and being movasaid second valve member is closely spaced to said ble between a closed position wherein said valve p r i i means; and head engages said second valve seat and an op said seal means are resilient seal means, one seal position wherein said valve head is out of engagemeans being Carried y Said Partition ans and ment with said second valve seat but still extending extending around Said SeQOnd Valve member, and through said partition means; one seal means being carried by and around said a hold means carried on said second valve member pisto" head between Said Piston head and Said on the first inlet port side of said partition means; 10 i i seal means thereby P g second resilient means associated with said second resmcted flow Passages between 5am seal valve member hold means, said second resilient means and Secmd valve member and between said seal means and housing. 4. A gas lift valve according to claim 3 wherein said seal means are formed from polytetrafluoroethylene.

5. A gas lift valve according to claim 3 wherein said second valve member carries a support shoulder therearound intermediate said pressure responsive means and said hold means, said support shoulder facing toward said pressure responsive means and touching said pressure responsive means when said second valve member and said pressure responsive means are in a contacting position; and at least one spacing ring fitting around said second valve member and abutting said support shoulder, said at least one spacing ring separating said support shoulder from said pressure responsive means when said second valve member and said pressure means being biased to urge said second valve member into the open position;

pressure responsive means carried by said housing engageable with but not connected with said second valve member opposite from the valve head and arranged to urge said second valve member into the closed position, said pressure responsive means being exposed to fluid pressure through said first inlet port, said pressure responsive means being movable from contact with said second valve member while leaving said second valve member in the closed position; and

seal means carried by said partition means and by said piston head to define a semi-sealed zone between said partition means and said piston head,

said seals forming an imperfect seal through which responsive means are in a contacting posmpm pressure can gradually leak. 6. A gas lift valve according to claim 1 wherein said 2. A gas lift valve acco din to l i 1 h i id first resilient means is a helical spring encircling said piston head has a shoulder facing toward said valve first Valve f l h d; said second resilient means is a helical spring encirsaid first resilient means is carried intermediate said Cling Said Second valve: member; and

valve h d d Said ld and said pressure responsive means is a bellows said hold means on said second valve member is an diaphragm havmg interior p y connected axially adjustable flange on one side of which abuts a Pressure domesaid second resilient means. 

1. A gas lift valve comprising, a housing having an outlet passage, a first inlet port spaced from said outlet passage, and a second inlet port spaced intermediate said first inlet port and said outlet passage; partition means intermediate said first inlet port and said second inlet port, said partition means having an axial passage therethrough; a first valve seat intermediate said second inlet port and said outlet passage, said seat having an axial bore therethrough; a first valve member having a valve head on one end and being movable between a closEd position wherein said valve head engages said first valve seat and an open position wherein said valve head is out of engagement with said first valve seat, the end of said valve member opposite said valve head being a piston head, said piston head being spaced from said partition when said first valve member is in either the opened or closed position, said valve member, piston head, and valve head having an axial bore therethrough; first resilient means associated with said first valve member, said first resilient means being biased to urge said first valve member into the open position; a second valve seat carried by said first valve member piston head on the side of said piston head nearest said partition means, said second valve seat having an axial bore therethrough in alignment with the bore in said first valve member; a second valve member having a valve head on one end, said second valve member extending through the bore of said partition means and being movable between a closed position wherein said valve head engages said second valve seat and an open position wherein said valve head is out of engagement with said second valve seat but still extending through said partition means; a hold means carried on said second valve member on the first inlet port side of said partition means; second resilient means associated with said second valve member hold means, said second resilient means being biased to urge said second valve member into the open position; pressure responsive means carried by said housing engageable with but not connected with said second valve member opposite from the valve head and arranged to urge said second valve member into the closed position, said pressure responsive means being exposed to fluid pressure through said first inlet port, said pressure responsive means being movable from contact with said second valve member while leaving said second valve member in the closed position; and seal means carried by said partition means and by said piston head to define a semi-sealed zone between said partition means and said piston head, said seals forming an imperfect seal through which pressure can gradually leak.
 2. A gas lift valve according to claim 1 wherein said piston head has a shoulder facing toward said valve head; said first resilient means is carried intermediate said valve head and said shoulder; and said hold means on said second valve member is an axially adjustable flange on one side of which abuts said second resilient means.
 3. A gas lift valve according to claim 2 wherein said piston head is closely spaced to said housing and said second valve member is closely spaced to said partition means; and said seal means are resilient seal means, one seal means being carried by said partition means and extending around said second valve member, and one seal means being carried by and around said piston head between said piston head and said housing, said seal means thereby forming restricted fluid flow passages between said seal means and second valve member, and between said seal means and housing.
 4. A gas lift valve according to claim 3 wherein said seal means are formed from polytetrafluoroethylene.
 5. A gas lift valve according to claim 3 wherein said second valve member carries a support shoulder therearound intermediate said pressure responsive means and said hold means, said support shoulder facing toward said pressure responsive means and touching said pressure responsive means when said second valve member and said pressure responsive means are in a contacting position; and at least one spacing ring fitting around said second valve member and abutting said support shoulder, said at least one spacing ring separating said support shoulder from said pressure responsive means when said second valve member and said pressure responsive means are in a contacting position.
 6. A gas lift valve according to claim 1 wherein said first resilient means is a helical spring encircling said first valve member; said second resilient means is a helical spring encircling said second valve member; and said pressure responsive means is a bellows diaphragm having its interior openly connected to a pressure dome. 